This invention relates generally to micro-machined three-dimensional structures, and in particular to micro-machined mirrors for use in optical readers, such as bar code readers or scanners.
Conventional bar code scanners are used to scan a surface with a laser beam. Conventional bar code scanners further typically utilize mirrors that are oscillated to permit the laser beam to scan. Conventional mirrors for bar code scanners are relatively large and imprecise.
In order to manufacture smaller and more precise bar code mirrors, micro-machining processes have been used in which a silicon substrate is micro-machined to produce a mirror. However, conventional micro-machined mirrors and their manufacturing processes suffer from a number of limitations. Prior art micro-machined mirrors do not provide appropriate compliance in all directions of the movement of the mirror. Such mirrors typically are not sufficiently shock resistant or able to operate over wide ranges of temperature over extended use.
Various known devices include a dual axis mode of operation whereby a mirror is rotated about a primary and a secondary axis. The typical device, however, requires a dual gimbaled structure having a gimbaled mirror coupled to a gimbaled support structure. The use of multiple gimbal couplings suffers from high cost and complex manufacturing. Typical devices attempting dual axis operation utilizing typical single point gimbal would suffer from component fatigue due to high material stress associated with the gimbal bending movements that result from rotational movement of the mirror about a secondary axis. Also, these single-gimbal dual axis devices typically suffer from compromised performance in terms of limited degree of rotational angle about the secondary axis per unit of driving force (e.g. electrostatic or magnetic).
The present invention provides micro-machined mirror devices which overcome one or more limitations of the existing micro-machined devices.
According to one aspect of the present invention, a mirror assembly is provided that includes a mass having having a first axis and a second axis, a pair of T-shaped hinges attached to a support structure supporting said mass, each T-shaped hinge having a first leg member attached to the mass and a T-member attached to the leg and to the support structure at opposite ends of the T-member, said T-member and leg member capable of torsional and translational movement, and at least two devices operatively associated with the mass and located to apply force to the mass, the capable of rotating the mass about the to rotate the mass about the first and second axes.
According to another aspect of the present invention, a method is provided for supporting a mass. The method includes supporting the mass with a pair of T-shaped hinges attached to a support structure, each T-shaped hinge having a first leg member attached to the mass and a T-member attached to the leg and to the support structure at opposite ends of the T-member, said T-member and leg member capable of torsional and translational movement, oscillating the mass about a first axis with at least two devices capable of applying force to the mass, and oscillating the mass about a second axis with the at least two devices.